The present invention relates in general to reinforcing cords made of several metal wires for reinforcing elastomeric products such as wires and in particular in relates to such a cord which is provided with at least one wrapping wire coiled thereon.
Such a reinforcing cord is known from the German Pat. No. 803,801. The wrapping wire in this known cord has the function to hold the constituent strands together and prevent dejoining of steel wires in the strands. The wrapping wire itself, however, does not contribute to the overall tensioning strength of the reinforcing cord. When a cord of this kind is embedded in an elastomeric material, for example, in a pneumatic tire of a vehicle, then in loading this material the risk of brinnelling or fretting corrosion will result. The fretting corrosion is one of the causes which lead to the shortening of service life of elastomeric products reinforced by the cords.
The risk of fretting corrosion is always present when two metal surfaces are in contact and subject to minute mutual shifting when under load. During the dynamic loading of reinforced elastomeric products such a condition occurs between the metallic wires of the cord which takes up the load of the product and the helical wrapping wire wound in contact with the steel wires.